buildlog.net

Instructables.com has a competition to design a cheap machine to make your own 3D printer filament from ABS or PLA pellets.

http://www.buildlog.net/blog/2012/05/fi ... ition-40k/

This is a fantastic initiative, i'd love to support it too.
Though I have no time to physically work on any such project directly for several months at this rate,
It would be great to see a community discussion develop here on this-
As we've seen with the extruder discussion, there's a lot of really bright folks here with some great ideas and talent;
Together, with a little out of the box ingenuity and teamwork, I'm sure an excellent candidate design would surface.
I'm already getting some ideas towards that...

I think the problem with the whole idea is in general, commercial extruders use a screw with a pitch that isn't constant, and trying to replicate that for under $250 is going to be difficult. It will be very interesting to see what people come up with.

I can see myself build one too, once the contest is over. Being able to make your own filament for your own 3D printer would be fantastic.

Variable pitch screw... hmmm. Got a picture of one?

Enraged wrote:I think the problem with the whole idea is in general, commercial extruders use a screw with a pitch that isn't constant, and trying to replicate that for under $250 is going to be difficult. It will be very interesting to see what people come up with.

I can see myself build one too, once the contest is over. Being able to make your own filament for your own 3D printer would be fantastic.

Yea I think the screw is out because of cost.

Is it possible to melt the pellets in a temperature controlled kettle with an agitator (to mix die). (One note is that a vacuum might be needed in most designs to remove air bubbles) But getting the liquid resin out of the kettle/pressure cooker into a consistent filament will be an interesting challenge.

Yeah, a picture would be nice! I did not find anything using "variable pitch screw", that would make me feel safe I have gotten the screw being discussed here.

No pics needed, really. Extruders often have screws that start up as a high-pitch spiral, then gradually shift to lower and lower pitch the closer to the mixing chamber / nozzle they get. See for example: http://www.spirex.com/media/doc/The%20B ... Design.pdf

It's what gives the extruder appropriate material compression. There are other, more complicated arrangements as well, with the pitch shifting back and forth etc.

Anyways, re: Filament Extruder Competition, there's already been a successful Kickstarter project doing the exact same thing: http://www.kickstarter.com/projects/roc ... ment-maker

Hello all.
Just chiming in about variable pitch screws; There are actually two very easy ways to build them for well under target cost here. I have done R&D in industrial automation for a lot of years now, and this is something I have experience with from past commercial projects. Both methods are easily scaled and suited even to small scale production. Its not that hard, just too technically intensive to cover in a forum post.
While not interested in developing and testing a complete entry for this competition - I have other projects at hand right now and limited time - I would not be averse to collaborating with a serious team on their project if variable pitch screws are a necessity, or of simply constructing VP screws to a teams specs for interested teams.

Another contender showed up on HackaDay. http://hackaday.com/2012/10/22/finally-turning-plastic-pellets-into-3d-printer-filament/